Biology subjects

Imhof, F.

Publications and source records attributed to Imhof, F..

4 recordsLinked to original sources

bioRxiv2025

The Reinstatement of a Forgotten Infantile Memory

Infantile memories present a striking paradox: while early-life experiences are typically forgotten, reflecting the phenomenon of infantile amnesia, traumatic events from infancy can profoundly shape adult cognition and behavior. How do memories that are seemingly inaccessible persistently influence cognitive processes and behaviors throughout life? Rodent studies have demonstrated that forgotten infantile memories remain encoded as latent "infantile memory engrams" (iEngrams) within neuronal circuits, capable of memory reinstatement under artificial experimental conditions. Still, the network mechanisms underpinning the natural reinstatement of a forgotten infantile memory are unknown. Here, we show that infantile memories, though physiologically irretrievable in adults, remain stored within hippocampal circuits and their engrams contribute to hippocampal network dynamics. Crucially, reinstating these memories requires a carefully orchestrated network process. An initial contextual reminder primes the hippocampal network to increase activity of the iEngram during a subsequent aversive reminder, which tags iEngram neurons for offline reactivation. This reactivation facilitates the integration of previously latent infantile memories with novel neuronal ensembles, reinstating behavior consistent with the original memory. These findings critically advance our understanding of the neuronal mechanisms underlying physiological memory encoding, retrieval, and reinstatement across development. Furthermore, they delineate the temporal boundaries and underlying physiological substrate of the process by which a latent representation becomes associated with a novel neuronal substrate, suggesting potential interventions to prevent the maladaptive reinstatement of traumatic infantile memories.

neuroscience↗

bioRxiv2023

Divergent Recruitment of Developmentally-Defined Neuronal Ensembles Supports Memory Dynamics

Memories are dynamic constructs whose properties change with time and experience. The biological mechanisms underpinning these dynamics remain elusive, particularly concerning how shifts in the composition of memory-encoding neuronal ensembles influence a memory properties evolution over time. By leveraging a developmental approach to target distinct subpopulations of principal neurons, we show that memory encoding results in the concurrent establishment of multiple memory traces in the mouse hippocampus. Two of these traces are instantiated in subpopulations of early- and late-born neurons and follow distinct reactivation trajectories post-encoding. Notably, the divergent recruitment of these subpopulations underpins memory ensembles gradual reorganization, and modulates memory persistence and plasticity across multiple learning episodes. Thus, our findings reveal profound and intricate relationships between ensemble dynamics and memories progression over time.

neuroscience↗

bioRxiv2020

Visual intracortical and transthalamic pathways carry distinct information to cortical areas

Sensory processing involves information flow between neocortical areas, assumed to rely on direct intracortical projections. However, cortical areas may also communicate indirectly via higher-order nuclei in the thalamus, such as the pulvinar or lateral posterior nucleus (LP) in the visual system. The fine-scale organization and function of these cortico-thalamo-cortical pathways remains unclear. We find that responses of mouse LP neurons projecting to higher visual areas likely derive from feedforward input from primary visual cortex (V1) combined with information from many cortical and subcortical areas, including superior colliculus. Signals from LP projections to different higher visual areas are tuned to specific features of visual stimuli and their locomotor context, distinct from the signals carried by direct intracortical projections from V1. Thus, visual transthalamic pathways are functionally specific to their cortical target, different from feedforward cortical pathways and combine information from multiple brain regions, linking sensory signals with behavioral context.

neuroscience↗

bioRxiv2017

A single-cell anatomical blueprint for intracortical information transfer from primary visual cortex

The wiring diagram of the neocortex determines how information is processed across dozens of cortical areas. Each area communicates with multiple others via extensive long-range axonal projections 1-6, but the logic of inter-area information transfer is unresolved. Specifically, the extent to which individual neurons send dedicated projections to single cortical targets or distribute their signals across multiple areas remains unclear5,7-20. Distinguishing between these possibilities has been challenging because axonal projections of only a few individual neurons have been reconstructed. Here we map the projection patterns of axonal arbors from 591 individual neurons in mouse primary visual cortex (V1) using two complementary methods: whole-brain fluorescence-based axonal tracing21,22 and high-throughput DNA sequencing of genetically barcoded neurons (MAPseq)23. Although our results confirm the existence of dedicated projections to certain cortical areas, we find these are the exception, and that the majority of V1 neurons broadcast information to multiple cortical targets. Furthermore, broadcasting cells do not project to all targets randomly, but rather comprise subpopulations that either avoid or preferentially innervate specific subsets of cortical areas. Our data argue against a model of dedicated lines of intracortical information transfer via \"one neuron - one target area\" mapping. Instead, long-range communication between a sensory cortical area and its targets may be based on a principle whereby individual neurons copy information to, and potentially coordinate activity across, specific subsets of cortical areas.

neuroscience↗